Xbee Wireless Kit (Chip Antenna)

This is a complete XBee wireless communication kit with everything you need to get up and running quickly, including 2 1mW XBee modules with chip antenna, the popular USB XBee Explorer, an XBee shield as well as headers required for the XBee shield. The very popular 2.4GHz XBee modules from Digi (formally Maxstream) take the 802.15.4 stack (the basis for Zigbee) and wrap it into a very simple to use serial command set. These modules allow a very reliable and simple communication between microcontrollers, computers, systems, really anything with a serial port! Point to point and multi-point networks are supported.
 The goal for this complete XBee Kit is to make wireless communication simple. Connect one XBee to the shield and your Arduino, connect the other XBee to the Explorer board and your computer, and you'll be able to seamlessly pass serial data to and from your Arduino wirelessly! Using this connection, you can transmit remote sensor data, or send data from your computer to update a scoreboard, or drive a robot from your keyboard! [...] Read more

6V backup battery power supply regulator with IC 7805

This simple and cheap 6 volt power supply circuit with 6V backup battery system.
The AC power 220V is entered to through input of transformer-T1 to reduce voltage as 9VAC, then wire connected to four diode D1-D4 as bridge rectifier became to 11VDC, then the current is filtered to dc voltage that low ripple output and then the voltage is regulated to 6VDC constant voltage by IC-KA7805( IC-7805 type) In normal it is used for 5 volt only but now we add two resistor to determined output voltage is 6 volt and passed through diode 1N4002-D6 to output is 6 volt.

Read more source: http://www.eleccircuit.com/6v-backup-battery-power-supply-regulator-with-ic-7805/